
package com.jstarcraft.ai.jsat.clustering.evaluation.intra;

import java.util.List;

import com.jstarcraft.ai.jsat.DataSet;
import com.jstarcraft.ai.jsat.classifiers.DataPoint;
import com.jstarcraft.ai.jsat.linear.distancemetrics.DistanceMetric;
import com.jstarcraft.ai.jsat.linear.distancemetrics.EuclideanDistance;

/**
 * Evaluates a cluster's validity by returning the maximum distance between any
 * two points in the cluster.
 * 
 * @author Edward Raff
 */
public class MaxDistance implements IntraClusterEvaluation {
    private DistanceMetric dm;

    /**
     * Creates a new MaxDistance measure using the {@link EuclideanDistance}
     */
    public MaxDistance() {
        this(new EuclideanDistance());
    }

    /**
     * Creates a new MaxDistance
     * 
     * @param dm the metric to measure the distance between two points by
     */
    public MaxDistance(DistanceMetric dm) {
        this.dm = dm;
    }

    /**
     * Copy constructor
     * 
     * @param toCopy the object to copy
     */
    public MaxDistance(MaxDistance toCopy) {
        this(toCopy.dm.clone());
    }

    @Override
    public double evaluate(int[] designations, DataSet dataSet, int clusterID) {
        double maxDistance = 0;
        for (int i = 0; i < dataSet.size(); i++)
            for (int j = i + 1; j < dataSet.size(); j++)
                if (designations[i] == clusterID)
                    maxDistance = Math.max(dm.dist(dataSet.getDataPoint(i).getNumericalValues(), dataSet.getDataPoint(j).getNumericalValues()), maxDistance);
        return maxDistance;
    }

    @Override
    public double evaluate(List<DataPoint> dataPoints) {
        double maxDistance = 0;
        for (int i = 0; i < dataPoints.size(); i++)
            for (int j = i + 1; j < dataPoints.size(); j++)
                maxDistance = Math.max(dm.dist(dataPoints.get(i).getNumericalValues(), dataPoints.get(j).getNumericalValues()), maxDistance);

        return maxDistance;
    }

    @Override
    public MaxDistance clone() {
        return new MaxDistance(this);
    }

}
